1. Field of the Invention
The present invention relates to an automotive windshield washer pump designed to jet a rinsing fluid onto an automotive windshield to assist a windshield wiping operation.
2. Description of the Prior Art
The automotive windshield washer system now in use in automotive vehicles generally comprises at least one windshield wiper adapted to be driven by a drive unit to move back and forth across the windshield, a windshield washer pump having an inlet and an outlet, at least one jetting nozzle generally disposed on a bonnet and fluid-connected with the outlet of the washer pump for jetting a rinsing fluid onto the windshield, and a container or tank for accommodating a quantity of the rinsing fluid and fluid-connected with the inlet of the washer pump.
It is well understood that, when foreign matter such as, for example, sand particles, enter the container in admixture with the rinsing fluid being filled in the container, it may be sucked into the washer pump during an operation of the washer pump, thereby damaging an impeller used in the washer pump. Once the impeller is damaged, problems would occur in that the washer pump may operate erroneously and that the jetting nozzle may be clogged. In either case, the rinsing fluid will no longer be jetted satisfactorily onto the windshield.
The Japanese Laid-open Utility Model Publication No. 2-60659, published May 7, 1990, discloses a solution to the foregoing problems. This will now be discussed with reference to FIG. 7.
According to that publication, the windshield washer system comprises a tank having a pump mounting hole 1a defined in a portion of the side wall 1 thereof adjacent the bottom of the tank. A generally tubular grommet 2 having outer and inner open ends 2a and 2b is inserted into the pump mounting hole 1a with the inner open end 2b protruding into the tank. An inlet nipple 3 that communicates with the inlet of the washer pump is fluid-tightly inserted into the grommet 2 through the outer open end 2a thereof. The inlet nipple 3 may be either an integral part of a pump casing forming the washer pump or a member separate therefrom.
The grommet 2 has an inner peripheral surface formed with an annular groove 2c extending circumferentially thereof and positioned adjacent the inner open end 2b thereof, and a filter member 4 is installed inside the grommet 2 with its outermost peripheral edge portion 4a received in the annular groove 2c.
According to the above mentioned publication, use is made of the filter member 4 to avoid any possible entry of the foreign matter from the tank into the washer pump. It has, however, been found that the solution suggested by the above mentioned publication poses the following problems.
(1) Although no foreign particles contained within the tank will substantially pass through the filter member 4, they tend to pile up around an outer peripheral portion of the filter member 4 adjacent the inner peripheral surface of the grommet 2. Once this occurs, the effective cross-sectional area of the filter member 4 which is utilized for the passage of the rinsing fluid therethrough is essentially reduced, hampering a smooth flow of the rinsing fluid from the tank towards the washer pump. In some cases, the effective cross-sectional area of the filter member 4 may be reduced so considerably as to result in an insufficient jetting of the rinsing fluid.
(2) Since the solution suggested by the above mentioned publication is such that, while the bore size of the inlet nipple 3 is defined according to the pumping capacity of the washere pump, the filter member 4 is installed inside the grommet 2 which receives the inlet nipple 3, the inner diameter of the inlet nipple 3 and the diameter of an inner portion 4b of the filter member 4 positioned radially inwardly of the outermost peripheral edge portion 4a are substantially equal to each other. In other words, the effective cross-sectional area of the filter member 4, which is represented by the total surface area of meshes or interstices of the inner portion 4b of the filter member 4 through which the rinsing fluid can flow, becomes smaller than the cross-sectional area of the bore of the inlet nipple 3. Accordingly, the provision of the filter member 4 in the manner described above causes a problem in that a rated flow of the rinsing fluid defined by the bore size of the inlet nipple 3 will not flow towards the washer pump, accompanied by a substantial reduction in pumping capacity of the washer pump. This is turn brings about a reduction in the amount of the rinsing fluid to be jetted onto the windshield.
(3) As a matter of course, a replenishment of a quantity of rinsing fluid is required when the tank is emptied. At the time of replenishment, air is trapped within a space S inside the grommet 2 and delimited between the filter member 4 and the inlet nipple 3. When the rinsing fluid is supplied into the tank through a supply port while the air is trapped within the space S, no rinsing fluid being supplied into the tank will flow towards a pump chamber through the interstices or meshes in the inner portion 4b of the filter member 4 due to a surface tension acting in those interstices or meshes between the rinsing fluid and the air. Therefore, even though the tank has been filled with the rinsing fluid, the air trapped between the filter member 4 and the inlet nipple 3 may hamper a smooth supply of the rinsing fluid towards the pump chamber even though the washer pump is subsequently operated. Specifically, where the washer pump is of a centrifugal type wherein the fluid medium is supplied by the action of a centrifugal force, the presence of the trapped air hampers a smooth supply of the rinsing fluid under pressure towards the nozzle. Under these circumstances, the washer pump tends to run idle without the air being discharged, failing to accomplish a proper jetting of the rinsing fluid.